Lipopolysaccharides (LPSs) are major, indispensable cell surface components of Gram-negative bacteria that have diverse roles in bacterial pathogenesis of plants. Environmental strains of Burkholderia cepacia have been described as phytopathogens, growth promotors, biocontrol agents and bioremediation agents. We have previously shown that LPSs from B. cepacia can be recognized as microbe-associated molecular pattern molecules, to elicit defense responses in plants. Recent findings suggest that the lipid A moiety might be partially responsible for LPSs perception. These studies were extended by analysis of the structure and biological activity of the lipid A moiety of LPSs of B. cepacia(.) The full structure was determined by a combination of negative/positive-ion matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) on intact and partially degraded substrates. B. cepacia lipid A was found to contain a tetra- or penta-acylated, 1,4'-diphosphorylated, β-(1-6)-linked D-GlcN disaccharide and further substituted by L-Ara4N in position 4'. As primary fatty acids, R-configurated 16:0(3-OH) (amide-linked in 2 and 2') and 14:0(3-OH) (ester-linked in 3 and 3', nonstoichiometric) were identified. A secondary 14:0 was located at position 2'. Its biological activity to elicit defense-related responses was subsequently investigated by monitoring the changes in the transcriptome of Arabidopsis thaliana seedlings. Genes found to be upregulated code for proteins involved in signal perception and transduction, transcriptional regulation, defense and stress responses. Furthermore, genes encoding proteins involved in chaperoning, protein interactions and protein degradation were differentially expressed as part of the metabolic reprogramming of cellular activities in support of immunity and defense.
Lipopolysaccharide, structure, Burkholderia cepacia, lipid A, plant basal resistance
NCBI PubMed ID: 20943675Journal NLM ID: 9104124Publisher: IRL Press at Oxford University Press
Correspondence: idubery@uj.ac.za
Institutions: Department of Biochemistry, University of Johannesburg, Kingsway Campus, Johannesburg, South Africa, Dipartimento di Chimica Organica e Biochimica, Universita’ di Napoli Federico II, via Cintia 4, I-80126 Napoli, Italy
Methods: 13C NMR, 1H NMR, GLC-MS, PCR, DNA sequencing, dephosphorylation, 31P NMR, MALDI-TOF MS, bioinformatic analysis
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